It is becoming clear today that mental disorders are a scientific reflection of the biological abnormalities in the brain. However, notwithstanding the growing understanding of brain anatomy and function, which allows at time a post-mortem diagnosis of a mental disorder, for most mental disorders there are no available objective assays which will allow their diagnosis in living individuals. Psychiatrists or neurologists when attempting to diagnose a mental disorder, have to rely on a series of tests, which very often cannot be interpreted unequivocally. Such a test series is generally a tedious process and there are thus no effective means available today to a practitioner, for a large scale screening of mental disorders.
Schizophrenia is one of the most severe and prevalent mental disorders. Due to its varied symptomatology and to its complex etiology, it is still debatable whether schizophrenia represents a distinct mental disorder, or several different mental diseases grouped under a common name.
A correlation between the occurrence of schizophrenia and the occurrence of various physiological phenomena has been found, but the relevancy of these phenomena to the disease's etiology is still debatable.sup.1-3. Despite lack of consistent experimental evidence, hypotheses concerning the involvement of autoimmune elements in schizophrenia have been suggested.sup.4-7. However, positive indication to the presence of autoantibodies in schizophrenic patients were obtained only in about 25% of tested patients.sup.4,5.
The existence of elevated levels of autoantibodies on blood platelets of both schizophrenic and demented patients has been reported recently.sup.8. In that study, the level of autoantibodies present on the surfaces of blood platelets (termed hereinafter "platelet associated antibodies" (PAA)) isolated from schizophrenic patients, patients with other effective mental disorders, dementia patients, (both treated with neuroleptics and untreated) and normal control subjects was determined by the use of anti-human IgA, IgE, IgG and IgM antibodies. The results of this study demonstrated that schizophrenic patients and demented patients had on the average about twice the level of PAA as compared to age-matched normal controls. Notwithstanding this statistically significant difference in the level of PAA between schizophrenic and demented patients versus normal controls, the difference was too small to serve as a basis for diagnosis of schizophrenia or dementia, or for screening populations for these mental disorders owing to the high proportion of both false positive and false negative results.